Musnad Ahmad Hadith 21780

Abu Sha’tha says that once I set out with the intention of performing Hajj. When I entered the Sacred House (the Ka’bah) and reached between two pillars, I went and clung to a wall. In the meantime, Ibn Umar (may Allah be pleased with them both) arrived and, standing by my side, performed four rak’ahs. When he finished the prayer, I asked him, “Where did the Noble Prophet (ﷺ) pray inside the Ka’bah?” He pointed to a place and said, “Here. Usamah bin Zaid (may Allah be pleased with him) informed me that the Noble Prophet (ﷺ) prayed here.” I asked him, “How many rak’ahs did the Noble Prophet (ﷺ) pray?” Ibn Umar (may Allah be pleased with them both) replied, “This is what I have been reproaching myself for until today, that I spent a long time with him but did not ask how many rak’ahs the Noble Prophet (ﷺ) prayed.” The next year, I again set out with the intention of Hajj and stood at the same place where I had stood the previous year. In the meantime, Abdullah bin Zubair (may Allah be pleased with him) arrived and stood by my side. Then he kept pushing me until he made me leave that place, and then he performed four rak’ahs there.